Wafer transport system and method for transporting wafers

ABSTRACT

A wafer transport device is moved on a transport rail, and stopped above a load port having a top surface. A light beam is projected onto the top surface of the load port, and image of the top surface is and the light beam is captured. A position of the hoist unit of the wafer transport device is aligned with respect to a position of the load port according to the image. The hoist unit is lowered toward the load port.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims priority to U.S. Provisional Application Ser.No. 62/772,947, filed Nov. 29, 2018, which is herein incorporated byreference.

BACKGROUND

In a wafer manufacturing process, wafers are processed multiple times atdifferent process chambers. Wafers are stored in wafer container unitssuch as a front opening unified pod or a wafer cassette. The wafercontainer units are temporarily positioned on load ports near certainprocess chambers, and moved from one load port to another. An automatedhandling system is used for transporting the wafer container unitsbetween process bays.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 shows a perspective view of a part of a wafer transport system, awafer container unit, and a semiconductor tool having a load port in asemiconductor fabrication facility (FAB) according to some embodimentsof the present disclosure.

FIG. 2 shows a side view of the wafer transport device and the wafercontainer unit in FIG. 1 according to some embodiments of the presentdisclosure.

FIG. 3 shows another schematic diagram of a wafer transport device inFIG. 1 according to some embodiments of the present disclosure.

FIG. 4A shows a flowchart of a method according to some embodiments ofthe present disclosure.

FIG. 4B shows a flowchart of a method according to some embodiments ofthe present disclosure.

FIGS. 5A and 5B show top views of a top surface of a hoist unit of FIG.1 according to some embodiments of the present disclosure.

FIGS. 6A and 6B show schematic diagrams of a belt wound around a beltwinding drum according to some embodiments of the present disclosure.

FIG. 7 shows a schematic diagram of a belt having belt markings woundaround a belt winding drum according to some embodiments of the presentdisclosure.

FIG. 8A shows a flowchart of a method according to some embodiments ofthe present disclosure.

FIG. 8B shows a flowchart of a method according to some embodiments ofthe present disclosure.

FIG. 9 shows a bottom view of the wafer transport device and the wafercontainer unit in FIG. 1 according to some embodiments of the presentdisclosure.

FIGS. 10A to 10D show top views of a top surface of a load port and atleast one light beam projection thereon according to some embodiments ofthe present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As used herein, “around”, “about”, “approximately”, or “substantially”shall generally mean within 20 percent, or within 10 percent, or within5 percent of a given value or range. Numerical quantities given hereinare approximate, meaning that the term “around”, “about”,“approximately”, or “substantially” can be inferred if not expresslystated.

The embodiments of this disclosure relate to wafer transport systems andmore specifically to wafer transport systems with hoist positionalignments and/or attitude inspections. The attitude of an object hereinis the orientation of the object with respect to a horizontal plane, andconsists of up to three components respectively in three axesperpendicular to each other. Because of the alignments and/orinspections, a wafer transport system with good alignment between awafer container unit and a corresponding load port (or a hoist of thewafer transport system) may be obtained. The wafer transport system maybe used in an automated material handling system (AMHS) that may includeat least one of overhead hoist transfer (OHT), overhead shuttle (OHS),rail guided vehicle (RGV), automated guided vehicle (AGV), personalguided vehicle (PGV), or combinations thereof.

FIG. 1 shows a perspective view of a part of a wafer transport system, awafer container unit 400, and a semiconductor tool 500 having a loadport 300 in a semiconductor fabrication facility (FAB) according to someembodiments of the present disclosure. In some embodiments, the FAB isdivided into various process bays (not shown) such as ion implantationbay, lithography bay, deposition bay, etching bay, diffusion bay, testbay and the like, each including multiple semiconductor tools with thesame or different functions, for performing various processes in chipfabrication. The wafer transport system transports wafers or reticlesbetween semiconductor tools either in the same process bay (i.e.intra-bay transportation) or between process bays (i.e. inter-baytransportation) during the fabrication process.

Referring to FIG. 1, in some embodiments of the present disclosure, thewafer transport system includes a network of transport rails 200 and awafer transport device 100 movably arranged on the transport rails 200.The transport rails 200 are configured to guide the movement of one ormore wafer transport device 100 supported and suspended from thetransport rails 200. In some embodiments, the transport rails 200 aremonorails that are mounted to and suspended from the ceiling of the FAB.It should be appreciated that the transport rails 200 may have anysuitable configuration so long as the wafer transport device 100 areappropriately supported from the transport rails 200 for rolling motion.

In some embodiments of the present disclosure, the transport rail 200 isconfigured to reach different parts of a wafer fabrication lab wherewafers are to be transported to. Load ports 300 can be selectivelyarranged under certain positions of the transport rail 200. Rail marks210 may be arranged on the transport rail 200 at positions above theload ports 300, and the wafer transport device 100 can further include amarking scanner and a controller 180 that are electrically connected.The marking scanner is directed toward the transport rail 200, andconfigured to scan the bottom surface of the transport rail 200. Whenthe wafer transport device 100 reaches a position on the transport rail200 having a rail mark 210, the marking scanner of the wafer transportdevice 100 scans the rail mark 210 and sends a signal corresponding tothe rail mark 210 to the controller 180 of the wafer transport device100. Depending on the signal sent from the marking scanner to thecontroller 180, the controller 180 can control the wafer transportdevice 100 to take a corresponding action. The actions can includestopping the wafer transport device 100 (thereby stopping the wafertransport device 100 above the corresponding load port 300), rotatingthe hoist unit 120 (thereby aligning the hoist unit 120 with anorientation of the load port 300), or a combination of the above.

In some embodiments of the present disclosure, the load port 300 has atop surface 301 for accommodating a wafer container unit 400, andprotrusions 310 on the top surface 301 for engaging the wafer containerunit 400 such that the wafer container unit 400 is secured when thewafer container unit 400 is disposed on the load port 300. Theprotrusions 310 of the load port 300 are male units for kinematiccoupling, and are configured to couple to corresponding grooves 420 on abottom side of the wafer container unit 400 (as show in FIG. 9). Asshown in FIG. 1, the three protrusions 310 are non-linear, and when thethree protrusions 310 are coupled to the three corresponding grooves 420of the wafer container unit 400, the wafer container unit 400 isrestricted in three degrees of freedom (i.e. linear motion in twohorizontal directions, and rotation about a vertical axis). Theprotrusions 310 do not restrict a vertical motion of the wafer containerunit 400, and the hoist unit 120 is free to raise and lower the wafercontainer unit 400 from and to the load port 300.

FIG. 2 shows a side view of the wafer transport device 100 and the wafercontainer unit 400 in FIG. 1 according to some embodiments of thepresent disclosure. The wafer transport device 100 is operable totransport wafer container units or reticle container units (hereinafterreferred to as “container units”) 400 throughout the FAB for intra-bayor inter-bay movement. Each wafer transport device 100 is configured andstructured to hold a wafer container unit 400 housing one or more wafersor reticles, and transport the wafer container unit 400 in a horizontalor lateral direction from one location to another within the FAB. Inaddition, each wafer transport device 100 is configured and operable topickup, raise/lower, hold, articulate, and release a wafer containerunit 400.

In some embodiments, the wafer container units 400 include standardmechanical interface (SMIF) pods which can hold a plurality of wafers(e.g. 200 mm or 8 inch), or front opening unified pods (FOUPs) which canhold larger wafers (e.g. 300 mm (12 inch) or 450 mm (18 inch)). Each ofthe wafer container units 400 may hold on the order of approximately 25wafers, for example. Alternatively or additionally, the wafer containerunits 400 may include other SMIF pods which can hold one or morereticles.

The wafer transport device 100 includes a main body 110, a plurality ofbelt winding drums 140 disposed on the main body 110, a plurality ofbelts 130, a plurality of winding cameras 150, and a hoist unit 120.Each one of the belts 130 has a drum end 131 connected to one of thebelt winding drums 140, and a hoist end 132 connected to the hoist unit120. The belts 130 are respectively wound around the belt winding drums140. A degree of winding of each one of the belts 130 refers to how muchof the belt 130 is wound around the respective belt winding drum 140. Ahigher degree of winding corresponds to a greater portion of the belt130 being wound around the belt winding drum 140. A smaller degree ofwinding corresponds to a smaller portion of the belt 130 being woundaround the belt winding drum 140. As shown in FIG. 2, when the belt 130has a high degree of winding, a smaller portion of the belt 130 hangsfrom the belt winding drum 140 of the wafer transport device 100, andthe distance between the hoist unit 120 and the belt winding drums 140is smaller. FIG. 3 shows another side view of the wafer transport devicein FIG. 1 according to some embodiments of the present disclosure. Asshown in FIG. 3, when the belt 130 has a small degree of winding, agreater portion of the belt 130 hangs from the belt winding drum 140 ofthe wafer transport device 100, and the distance between the hoist unit120 and the belt winding drums 140 is greater. Therefore, the height ofthe hoist unit 120 can be controlled by adjusting the degrees of windingof the belts 130 around the respective belt winding drums 140.

In some embodiments of the present disclosure, the hoist unit 120 has agripper 122 configured to grip or release the wafer container unit 400.Specifically, as shown in FIG. 2, the wafer container unit 400 has aflange 410 configured to be gripped by the gripper 122 of the hoist unit120. The wafer container unit 400 can be gripped by the hoist unit 120and transported along the transport rail 200 by the wafer transportdevice 100, and loaded onto or lifted from the load ports 300 arrangedat selected locations.

As shown in FIG. 1, when the wafer transport device 100 moves on thetransport rail 200, the degrees of winding of the belts 130 can be high,such that the hoist unit 120 is raised close to the main body 110 of thewafer transport device 100 and transported along the transport rail 200in a safe manner, within a vertical space VS in which the wafertransport device 100 can move without being obstructed by persons orequipment. In some embodiments of the present disclosure, the main body110 has a plurality of walls 112 and the hoist unit 120 can be raised toa position between the walls 112, such that the hoist unit 120 isaccommodated in the main body 110 of the wafer transport device 100. Inthis condition, the wafer container unit 400 gripped by the hoist unit120 is also accommodated in the main body 110 of the wafer transportdevice 100, such that the wafer container unit 400 is transported safelyinside the main body 110 and within the vertical space VS.

By adjusting the degrees of winding of the belts 130 of the wafertransport device 100, the height of the hoist unit 120 of the wafertransport device 100 can be adjusted. Specifically, the hoist unit 120can be lowered to grip and pick up the wafer container unit 400 from theload port 300, and raised along with the wafer container unit 400 to themain body 110, whereby the wafer container unit 400 can be transportedby the wafer transport device 100 along the transport rail 200. At atarget destination, the hoist unit 120 can be lowered to release thewafer container unit 400 onto the load port 300, and raised to the mainbody 110, whereby the wafer transport device 100 can await anothertransport assignment. The wafer container unit 400 can be transported bythe wafer transport device 100 from one load port 300 to another loadport 300.

In some embodiments of the present disclosure, when loading or unloadingthe wafer container unit 400 on the load port 300, the attitude of thehoist unit 120 is kept substantially the same as the attitude of theground such that wafers inside the wafer container unit 400 are notdisturbed. Specifically, the attitude of the hoist unit 120 herein is adirection of a line normal to a top surface 121 of the hoist unit 120,and the attitude of the ground is a direction of a line normal to theground (i.e. a vertical line). In some embodiments of the presentdisclosure, when loading or unloading the wafer container unit 400 onthe load port 300, the attitude of the hoist unit 120 is keptsubstantially the same as the attitude of the top surface 301 of theload port 300 (direction of a line normal to the top surface 301), so asto allow the wafer container unit 400 to successfully engage ordisengage the top surface 301 of the load port 300 in a smooth manner.In other words, the top surface 121 of the hoist unit 120 is keptparallel to a predetermined surface when the hoist unit 120 grips orreleases the wafer container unit 400. If the top surface 121 of thehoist unit 120 is not substantially parallel to the predeterminedsurface, then the wafer transport device 100 is sent to a maintenancearea for maintenance.

FIG. 4A shows a flowchart of a method M10 according to some embodimentsof the present disclosure. The method M10 is merely an example, and isnot intended to limit the present disclosure beyond what is explicitlyrecited in the claims. Additional operations can be provided before,during, and after the method M10, and some operations described can bereplaced, eliminated, or moved around for additional embodiments of theprocess. In some embodiments, the method M10 may be applied in a FAB.Specifically, the method M10 may be applied to, but should not belimited to, the wafer transport device 100 of FIG. 1. For clarity andease of explanation, some elements of the figures have been simplified.

In operation S12 of the method M10, a wafer transport device is movedtoward a process bay including a load port. Referring to FIGS. 1 and 4A,the wafer transport device 100 is suspended from the transport rail 200.The controller 180 of the wafer transport system controls the movementof the wafer transport device 100, such that the wafer transport device100 is moved on the transport rail 200.

The wafer transport device 100 is moved toward a process bay. Theprocess bay may be an ion implantation bay, lithography bay, depositionbay, etching bay, diffusion bay, test bay and the like, each includingmultiple semiconductor tools 500 with the same or different functions,for performing various processes in chip fabrication. The semiconductortools 500 may include any type of wafer processing, metrology,inspection, testing or other tools, and wafers or reticles storageequipment such as stockers used in semiconductor chip fabrication.

In some embodiments, each semiconductor tool 500 includes one or moreload ports 300 configured to support and dock the wafer container unit400 for facilitating insertion and removal of wafers or reticlesinto/from the semiconductor tool 500. As shown in FIG. 1, the load port300 is a plate structure extended from the semiconductor tool 500 andpositioned under the transport rail 200 of the wafer transport system soas to receive/support the wafer container unit 400.

In some embodiments, there are many rail marks 210 on the bottom surfaceof the transport rail 200. The marking scanner of the wafer transportdevice 100 senses the bottom surface of the transport rail 200 when thewafer transport device 100 is moving on the transport rail 200. When themarking scanner senses a predetermined rail mark 210, the wafertransport device 100 receives a stop demand from the controller 180.Hence, the wafer transport device 100 is stopped over the predeterminedload port 300. On the other hand, when the marking scanner sensesanother rail mark, the wafer transport system does not send a stopdemand to the wafer transport device 100. In this case, the wafertransport device 100 is still moving on the transport rail 200.

In operation S14 of the method M10, a hoist unit of the wafer transportdevice over the load port is lowered. Referring to FIGS. 3 and 4A, afterthe wafer transport device 100 is stopped over the predetermined loadport 300, the belt winding drums 140 rotate to unwind the belts 130. Assuch, the hoist unit 120 can be lowered to a predetermined level.

In operation S16 of the method M10, the attitude of the hoist unit isdetermined. Referring to FIGS. 3 and 4A, the attitude of the hoist unit120 depends on the lengths of the belts 130 hanging between therespective belt winding drums 140 and the hoist unit 120. The attitudeof the hoist unit 120 can be adjusted by adjusting the lengths of thebelts 130. The lengths of the belts 130 are kept substantially equal tomaintain a constant attitude for the hoist unit 120.

In some embodiments of the present disclosure, as shown in FIG. 3, theattitude of the hoist unit 120 is determined by measuring a firstdistance between a first position P1 of a top surface 121 of the hoistunit 120 and a bottom surface 111 of the wafer transport device 100,measuring a second distance between a second position P2 of the topsurface 121 of the hoist unit 120 and the bottom surface 111 of thewafer transport device 100, and comparing the first distance and thesecond distance. In some embodiments, the hoist unit 120 and apredetermined surface have substantially the same attitude when thefirst distance and the second distance are substantially the same. Thepredetermined surface can be the ground, or the top surface 301 of theload port 300, or both. As shown in FIG. 3, the wafer transport device100 further includes two distance sensors 170 arranged on the bottomsurface 111 of the wafer transport device 100. The distance sensors 170are directed toward the first position P1 and the second position P2 ofthe top surface 121 of the hoist unit 120. In some embodiments, thedistance sensors 170 are laser distance sensors or other suitablesensors.

FIGS. 5A and 5B show top views of the top surface 121 of the hoist unit120 of FIG. 1 according to some embodiments of the present disclosure.In some embodiments of the present disclosure, the hoist ends 132 of thebelts 130 are connected to the hoist unit 120 near four corners of thetop surface 121 of the hoist unit 120. Line L1 passes through the centerC of the top surface 121 of the hoist unit 120, and is parallel to twoedges of the top surface 121 of the hoist unit 120. Line L2 passesthrough the center C of the top surface 121 of the hoist unit 120, andis parallel to the other two edges of the top surface 121 of the hoistunit 120. Line L3 passes through the center C and the corners C1, C3opposite each other. Line L4 passes through the center C and the cornersC2, C4 opposite each other. The winding drum 140 connected to one of thebelts 130 and the hoist end 132 of said belt 130 has a distancetherebetween. When said belt 130 is connected to the top surface 121 ofthe hoist unit 120 at the corner C1, and said distance between thewinding drum 140 and the hoist end 132 corresponding to said belt 130 isshorter or longer than distances between the winding drums 140 and thehoist ends 132 corresponding to the other belts 130 connected at thecorners C1, C2, and C4, the corner C1 is respectively titled upward ordownward with respect to the rest of the top surface 121 of the hoistunit 120. Similarly, when one of the belts 130 is connected to the topsurface 121 of the hoist unit 120 at the corner C2, C3, or C4, and thedistance between the winding drum 140 and the hoist end 132corresponding to said belt 130 is shorter or longer than distancesbetween the winding drums 140 and the hoist ends 132 corresponding tothe other belts 130 connected at the other corners, the corner C2, C3,or C4 is respectively titled upward or downward with respect to the restof the top surface 121 of the hoist unit 120. Referring to FIG. 5A, whenthe corner C1 is tilted upward or downward, the first distance and thesecond distance are different if the first position and the secondposition of the top surface of the hoist unit are on different sides ofthe line L4. Similarly, when the corner C3 is tilted upward or downward,the first distance and the second distance are different if the firstposition and the second position on the top surface of the hoist unitare on different sides of the line L4. Similarly, when the corner C2 orthe corner C4 is tilted upward or downward, the first distance and thesecond distance are different if the first position and the secondposition on the top surface of the hoist unit are on different sides ofthe line L3.

When the adjacent corners C1 and C4 are both tilted upward or bothtilted downward with respect to the other two corners C2 and C3, thenthe first distance and the second distance are different if the firstposition and the second position on the top surface of the hoist unitare on different sides of the line L2. Similarly, when the adjacentcorners C1 and C2 are both tilted upward or both tilted downward withrespect to the other two corners C3 and C4, then the first distance andthe second distance are different if the first position and the secondposition on the top surface of the hoist unit are on different sides ofthe line L1.

Therefore, if the first position and the second position are ondifferent sides of the four lines L1, L2, L3, and L4, then the firstdistance and the second distance are different when the top surface ofthe hoist unit tilts toward any one or any two adjacent of the cornersC1, C2, C3, C4. In some embodiments of the present disclosure, the firstposition and the second position are on different sides of each of thefour lines L1, L2, L3, and L4. In other words, the four lines L1, L2,L3, L4 partition the top surface 121 of the hoist unit 120 into eightsections S1-S8, and the first position P1 and the second position P2 areon opposite sections, such as sections S1 and S5 as shown in FIG. 5A, orsections S3 and S7 as shown in FIG. 5B.

In some embodiments of the present disclosure, the attitude of the hoistunit 120 is determined by measuring a tension of each of the belts 130.Referring to FIG. 2, the wafer transport device 100 further includes atension sensor 160, and the tension of each of the belts 130 can bemeasured by using the tension sensor 160. In some embodiments, thetension sensor 160 may be an acoustic sensor configured to detect andanalyze sound waves from the belt 130. Specifically, when the hoist unit120 is lowered, the belts 130 will vibrate. The frequency of thevibration of the belt 130 depends on the length thereof. As such, thetension sensor 160 may sense the sound waves of the corresponding belt130, and the vibration frequency may be analyzed, e.g., via machinelearning, to determine the tension of the belt 130. The tension sensor160 may be arranged proximal to a portion of the belt 130 under stress,namely the portion of the belt 130 extending between the belt windingdrum 140 and the hoist unit 120. The tensions may be uneven when thehoist unit 120 is tilted toward one side or one corner. It is noted thatthe acoustic sensor mentioned above is an example, and should not limitthe scope of the present disclosure. Other suitable sensors may beapplied to this operation as long as the length of the belt 130 can bedetected.

In some embodiments of the present disclosure, data are fed to a machinelearning system to analyze relationship between vibration frequencies ofthe belts 130 and the tensions of the belts 130. Specifically, thevibration frequency of the belt 130 is measured by the acoustic tensionsensor 160, and the tension of the belt 130 is determined by anothersensor (e.g. a tension meter) or by inspecting the winding of the belt130 around the corresponding winding drum 140, and the vibrationfrequency and the tension of the belt 130 are fed as a related data pairto the machine learning system. The machine learning system analyzes aplurality of data pairs of related vibration frequencies and tensions,and derives a rule for associating specific vibration frequencies of thebelt 130 to specific tensions of the belts 130, respectively. Inoperation S18, S20, and S22 of the method M10, a response is providedaccording to the determined attitude. In some embodiments of the presentdisclosure, when the determined attitude of the hoist unit is not thesame as the attitude of a predetermined surface (e.g. the top surface ofthe load port, and/or the ground), the response includes raising thehoist unit (operation S18) and sending the wafer transport device to amaintenance area (operation S20). Specifically, the hoist unit 120 ofthe wafer transport device 100 may be inclined if the determinedattitude is not the same as the attitude of the predetermined surface.This inclined hoist unit 120 is sent to the maintenance area, and anattitude calibration is performed on the inclined hoist unit 120.

When the determined attitude of the hoist unit is the same as theattitude of the predetermined surface, the response includes operatingthe gripper 122 of the hoist unit to grip or release the wafer containerunit (operation 22). In some embodiments, the wafer container unit 400is initially disposed on the load port 300, and the hoist unit 120 maygrip the wafer container unit 400 after the attitude is determined to bethe same as the attitude of the predetermined surface. In some otherembodiments, the wafer container unit 400 is initially gripped by thehoist unit 120 and is transported using the wafer transport device 100.The hoist unit 120 may release the wafer container unit 400 on the loadport 300 after the attitude is determined to be the same as the attitudeof the predetermined surface.

FIG. 4B shows a flowchart of a method M10′ according to some embodimentsof the present disclosure. The method M10′ is merely an example, and isnot intended to limit the present disclosure beyond what is explicitlyrecited in the claims. Additional operations can be provided before,during, and after the method M10, and some operations described can bereplaced, eliminated, or moved around for additional embodiments of theprocess. The operations S12, S14, S16, S18, S20, and S22 of method M10′are the same as the operations S12, S14, S16, S18, S20, and S22 ofmethod M10, and the detailed description is omitted herein.

In operation S26 of method M10′, the hoist unit is raised. Referring toFIGS. 1 and 2, after the hoist unit 120 grips or releases the wafercontainer unit 400, the hoist unit 120 is raised by the controller 180for the next transporting mission. In some embodiments, the belt windingdrums 140 rotate, such that the belts 130 respectively wind the beltwinding drums 140 again, and the hoist unit 120 is raised to apredetermined level.

In operation S28 of method M10′, a degree of winding of at least onebelt around the belt winding drum is determined. FIGS. 6A and 6B showschematic diagrams of a belt 130 wound around a belt winding drum 140according to some embodiments of the present disclosure. In someembodiments of the present disclosure, at least one of the belts 130 hasa plurality of belt markings 133 on a side thereof. After the hoist unit120 is raised, an image of the belt markings 133 of the belt 130 iscaptured by the winding camera 150 positioned proximal to a portion ofthe belt 130 wound around the respective belt winding drum 140 as shownin FIG. 2. In some embodiments, the winding camera 150 is positioned todirectly face the side of the belt 130 formed with the belt markings 133as shown in FIGS. 6A and 6B. The positions of the belt markings 133 inthe captured image are compared to predetermined positions of the beltmarkings 133, so as to determine the degree of winding of the belt 130.In some embodiments, the predetermined positions of the belt markings133 may be determined by capturing an image of the belt markings 133when the corresponding wafer transport device 100 is new. Alternatively,the predetermined positions of the belt markings 133 may be determinedby capturing an image of the belt markings 133 after the attitude of thehoist unit 120 is properly calibrated.

In operation S30 of method M10′, the wafer transport device is moved toanother load port when the positions of the belt markings in the imageare consistent with the predetermined positions of the belt markings.That is, the wafer transport device 100 is in a good condition totransport wafer container units. In operation S32 of method M10′, thewafer transport device is sent to a maintenance area when the positionsof the belt markings in the image are inconsistent with thepredetermined positions of the belt markings. When the positions of thebelt markings 133 as shown in FIG. 6B are not the same as thepredetermined positions of the belt markings 133 as shown in FIG. 6A,the wafer transport device 100 is sent to the maintenance area torecalibrate the attitude of the hoist unit 120.

In some embodiments of the present disclosure, the belt markings 133 onthe side of the belt 130 form a line pattern when they are at theirrespective predetermined positions, as shown in FIG. 6A. The beltmarkings 133 align at every 180 degrees of the belt wrapped around thebelt winding drum 140. The belt distance between consecutive beltmarkings on the belt increases from the drum end 131 of the belt 130 tothe hoist end 132 of the belt 130. FIG. 7 shows a schematic diagram of abelt having belt markings 1331, 1332, and 1333 wound around a beltwinding drum 140 according to some embodiments of the presentdisclosure. Specifically, a diameter D1 is a straight distance betweenthe first belt marking 1331 and the second belt marking 1332, anddiameter D2 is a straight distance between the second belt marking 1332and the third belt marking 1333. The belt distance BD1 between a firstbelt marking 1331 and a second belt marking 1332 lies substantiallyalong a circular path, so is substantially equal to diameter D1 times πdivided by 2. Similarly, the belt distance BD2 between the second beltmarking 1332 and a third belt marking 1333 is substantially along acircular path, so is substantially equal to diameter D2 times π dividedby 2. The difference between diameter D1 and diameter D2 is about athickness T of the belt. Therefore, the difference between the beltdistance between the first and second belt markings 1331, 1332, and thebelt distance between the second and third belt markings 1332, 1333 isabout the thickness T times π divided by 2. Similarly, the belt distancefor each successive belt marking toward the hoist end increases by aboutthe thickness T times π divided by 2.

Note that the proportions of the belts shown in FIG. 6A, 6B, and FIG. 7are not necessarily precise, and may be exaggerated for purpose ofillustration. Specifically, the thickness of the belts is exaggeratedfor ease of description.

When loading or unloading the wafer container unit 400 on the load port300, the horizontal position and orientation of the hoist unit 120 maybe aligned to the horizontal position of the load port 300 so as toallow the wafer container unit 400 to successfully engage or disengagethe load port 300 in a smooth manner.

In some other embodiments, the method M10 (or M10′) further includescollecting an operating pulse of a motor of the wafer transport device.For example, the controller 180 may collect the operating pulse of themotor when the wafer transport device 100 moves on the transport rails200. The controller 180 may auto-learn the proper pulse range of themotor by using the collected operating pulses as a database. Thecontroller 180 may determine if the motor is abnormal (e.g., thetransport speed is too slow or too fast) by comparing the collectedoperating pulse to the proper pulse range. If the collected operatingpulse is out of the proper pulse range, the controller 180 willtransport the corresponding wafer transport device to the maintenancearea for maintenance.

In some other embodiments, the method M10 (or M10′) further includescollecting an operating temperature of the motor of the wafer transportdevice. For example, the controller 180 may collect the operatingtemperature of the motor when the wafer transport device 100 moves onthe transport rails 200. The controller 180 may auto-learn the propertemperature range of the motor by using the collected operatingtemperatures as a database. The controller 180 may determine if themotor is abnormal (e.g., the temperature of the moter is too high) bycomparing the collected operating temperature to the proper temperaturerange. If the collected operating temperature is out of the propertemperature range, the controller 180 will transport the correspondingwafer transport device to the maintenance area for maintenance.

FIG. 8A shows a flowchart of a method M20 according to some embodimentsof the present disclosure. The method M20 is merely an example, and isnot intended to limit the present disclosure beyond what is explicitlyrecited in the claims. Additional operations can be provided before,during, and after the method M20, and some operations described can bereplaced, eliminated, or moved around for additional embodiments of theprocess. In some embodiments, the method M20 may be applied in a FAB.Specifically, the method M20 may be applied to, but should not belimited to, the wafer transport device 100 of FIG. 1. For clarity andease of explanation, some elements of the figures have been simplified.

In operation S52 of the method M20, a wafer transport device 100 ismoved on a transport rail 200. Referring to FIGS. 1 and 8A, the wafertransport device 100 is suspended from the transport rail 200. Thecontroller 180 of the wafer transport system controls the movement ofthe wafer transport device 100, such that the wafer transport device 100is moved on the transport rail 200.

In operation S54 of the method M20, the wafer transport device 100 isstopped above the load port 300 having the top surface 301. In someembodiments, there are many rail marks 210 on the bottom surface of thetransport rail 200. The marking scanner of the wafer transport device100 senses the bottom surface of the transport rail 200 when the wafertransport device 100 is moving on the transport rail 200. When themarking sensor senses a predetermined rail mark 210, the wafer transportdevice 100 receives a stop demand from the wafer transport system.Hence, the wafer transport device 100 is stopped over the predeterminedload port 300. On the other hand, when the marking sensor senses anotherrail mark, the wafer transport system does not send a stop demand to thewafer transport device 100. In this case, the wafer transport device 100is still moving on the transport rail 200.

In some embodiments, the wafer transport device 100 may be stopped atthe wrong position because of inertia. For example, the wafer transportdevice 100 may be stopped past the predetermined position if the wafertransport device 100 was moving at a high speed. In this case, the wafertransport device 100 and the corresponding load port 300 are not alignedvertically. In some other embodiments, the orientation of the wafertransport device 100 is not aligned with the orientation of thecorresponding load port 300 when the wafer transport device 100 isstopped over the corresponding load port 300. The controller 180 maythus send a rotation demand to the wafer transport device 100 (accordingto the data stored in the rail mark 210) to rotate the wafer transportdevice 100 (as described in operation S58 in FIG. 8B). As such, theorientations of the wafer transport device 100 and the load port 300 maybe aligned. However, due to the law of inertia, the wafer transportdevice 100 may be over-rotated, and the orientations of the wafertransport device 100 and the load port 300 are misaligned again.

Due to the misalignment problems mentioned above, an alignment processmay be performed after the wafer transport device 100 is stopped. Inoperation S56 of the method M20, a light beam is projected onto the topsurface of the load port. FIG. 9 shows a bottom view of the wafertransport device 100 and the wafer container unit 400 in FIG. 1according to some embodiments of the present disclosure. In someembodiments of the present disclosure, at least one light beam projector190 is arranged on the main body 110 of the wafer transport device 100.The light beam projector 190 is configured to project a light beam ontothe top surface 301 of the load port 300. The light beam projected ontothe top surface 301 of the load port 300 can include a laser dot 910 asshown in FIG. 10A, a laser line 920 as shown in FIGS. 10B and 10D, ortwo laser lines 920, 930 as shown in FIG. 10C. In some embodiments, thelaser lines 920 and 930 are not parallel. In some embodiments, the laserlines 920 and 930 are substantially perpendicular.

In operation S62 of the method M20, an image of the top surface of theload port and the light beam is captured. The relative position betweenthe load port 300 and the wafer transport device 100 can be determinedfrom the captured image. Referring to FIG. 9, a load port camera 180 isarranged on the main body 110 of the wafer transport device 100, and isconfigured to capture an image of the top surface 301 of the load port300. As mentioned above and as shown in FIG. 1, the load port 300 hasthe protrusions 310 disposed on the top surface 301 thereof.Furthermore, the top surface 301 of the load port 300 has a plurality ofedges, e.g., four edges.

FIGS. 10A to 10D show top views of a top surface of a load port and atleast one light beam projection thereon according to some embodiments ofthe present disclosure. The captured image may include at least one ofthe protrusions 310, at least one edge 302 of the top surface 301 of theload port 300, and the light beam projected onto the top surface 301 ofthe load port 300. In some embodiments as shown in FIG. 10A, therelative positions of the laser dot 910 and the protrusion 310 of theload port 300 can be determined from the captured image. In someembodiments as shown in FIG. 10B, the relative positions of the laserline 920 and the protrusion 310 of the load port 300 can be determinedfrom the captured image. In some embodiments as shown in FIG. 10C, therelative positions of the laser lines 920, 930 and the protrusion 310 ofthe load port can be determined from the captured image. In someembodiments as shown in FIG. 10D, the relative orientation of the laserline 920 and the edge 302 of the top surface 301 of the load port 300can be determined from the captured image. In other words, an anglebetween the laser line 920 and the edge 302 of the top surface 301 ofthe load port 300 is determined from the captured image.

In operation S64 of the method M20, a position of a hoist unit 120 ofthe wafer transport device 100 is aligned with respect to a position ofthe load port 300 according to the image. For example, in FIG. 10A, in adefault setting, the load port 300 and the wafer transport device 100are aligned with each other when the laser dot 910 overlaps theprotrusion 310 of the load port 300. The captured image of FIG. 10Ashows the load port 300 and the wafer transport device 100 aremisaligned. Therefore, the wafer transport device 100 is movedhorizontally by the controller 180 until the laser dot 910 is on theprotrusion 310 of the load port 300. Similarly, in FIG. 10B, the defaultsetting is that the laser line 920 crosses the protrusion 310 of theload port 300. Therefore, the wafer transport device 100 is movedhorizontally by the controller 180 until the laser line 920 passesthrough the protrusion 310 of the load port 300. In FIG. 100, thedefault setting is that the laser lines 920 and 930 both cross theprotrusion 310 of the load port 300. Therefore, the wafer transportdevice 100 is moved horizontally by the controller 180 until each of thelaser lines 920, 930 passes through the protrusion 310 of the load port300. In FIG. 10D, the default setting is that the laser line 920 isparallel to one edge 302 of the top surface 301 of the load port 300.Therefore, the hoist unit 120 is rotated until the laser line 920 isparallel to the corresponding edge 302 of the top surface 301 of theload port 300.

It is noted that the default setting mentioned above are examples, andshould not limit the present disclosure. In some other embodiments, thedefault settings include the laser dot 910 overlapping with otherelements (such as another protrusion or one edge of the top surface301), the laser line 920 (930) crossing other elements (such as anotherprotrusion), the laser lines 920 (930) and an edge of the top surfaceforming an angle greater than 0 degrees, etc.

In operation S66 of the method M20, the hoist unit 120 is lowered towardthe load port 300. After the wafer transport device 100 is aligned withthe load port 300 by performing the alignments mentioned above, the beltwinding drums 140 rotate to unwind the belts 130. As such, the hoistunit 120 can be lowered to a predetermined level.

FIG. 8B shows a flowchart of a method M20′ according to some embodimentsof the present disclosure. The method M10′ is merely an example, and isnot intended to limit the present disclosure beyond what is explicitlyrecited in the claims. Additional operations can be provided before,during, and after the method M10, and some operations described can bereplaced, eliminated, or moved around for additional embodiments of theprocess. The operations S52, S54, S56, S62, S64, and S66 of method M20′are the same as the operations S52, S54, S56, S62, S64, and S66 ofmethod M20, and the detailed description is omitted herein.

In operation S58 of the method M20′, an orientation information of theload port 300 is acquired from the rail mark 210. In some embodiments,the rail mark 210 is a barcode having the orientation information of theload port 300 located there-below.

In operation S60 of the method M20′, the hoist unit 120 is rotated basedon the orientation information. In some embodiments, the hoist unit 120is rotated based on the orientation information, before operation S62wherein the image of the top surface 301 of the load port 300 iscaptured by the load port camera 180.

In operation S68 of the method M20′, after the hoist unit 120 isproperly aligned with the load port 300 in operation S66, the hoist unit120 is lowered toward the load port 300, and the wafer container unit400 gripped by or released from the hoist unit 120. Specifically, thegripper 122 of the hoist unit 120 is operated to grip or release thewafer container unit 400, and the wafer container unit 400 is loadedonto or picked up from the load port 300.

The present disclosure provides devices and methods for determining anattitude of the hoist unit, such that the wafer container unit can beloaded to and picked up from the load port by the hoist unit in a smoothmanner. Furthermore, the present disclosure provides devices and methodsfor determining an orientation and a horizontal position of the hoistunit with respect to the load port, such that the wafer container unitcan be loaded to and picked up from the load port by the hoist unit in asmooth manner.

According to some embodiments of the present disclosure, a wafertransport device is moved on a transport rail. The wafer transportdevice is stopped above a load port having a top surface. A light beamis projected onto the top surface of the load port. An image of the topsurface of the load port and the light beam is captured. A position of ahoist unit of the wafer transport device is aligned with respect to aposition of the load port according to the image. The hoist unit islowered toward the load port.

According to some embodiments of the present disclosure, a wafertransport device is moved toward a process bay comprising a load port. Ahoist unit of the wafer transport device above the load port is lowered.An attitude of the hoist unit is determined. A response is provided by acontroller, according to the determined attitude.

According to some embodiments of the present disclosure, a wafertransport system includes a transport rail, and a wafer transportdevice. The wafer transport device is movably arranged on the transportrail, and includes a main body, a plurality of belt winding drumsdisposed on the main body, a plurality of belts connected to and woundaround the respective belt winding drums, a plurality of winding camerasconfigured to capture images of the sides of portions of the belts woundaround the belt winding drums, and a hoist unit connected to theplurality of belts. Each of the belts has belt markings formed on a sideof the belt.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: moving a wafer transportdevice on a transport rail; stopping the wafer transport device above aload port having a top surface; projecting a light beam onto the topsurface of the load port; capturing an image of the top surface of theload port and the light beam; aligning a position of a hoist unit of thewafer transport device with respect to a position of the load portaccording to a position of the light beam projected on the top surfaceof the load port in the image; and lowering the hoist unit toward theload port.
 2. The method according to claim 1, wherein the load portfurther has a protrusion disposed on the top surface thereof, andaligning the position of the hoist unit with respect to the position ofthe load port comprises: determining a relative position of the lightbeam and the protrusion of the load port from the image; and moving thewafer transport device based on the relative position.
 3. The methodaccording to claim 1, wherein capturing the image of the top surface ofthe load port and the light beam comprises using a load port cameraarranged at a main body of the wafer transport device.
 4. The methodaccording to claim 1, wherein the light beam is a laser line, andaligning the position of the hoist unit of the wafer transport devicewith respect to the position of the load port comprises: determining anangle between the laser line and an edge of the top surface of the loadport from the image; and rotating the hoist unit based on the angle. 5.The method according to claim 1, wherein stopping the wafer transportdevice above the load port comprises: sensing the transport rail by thewafer transport device during moving the wafer transport device; andstopping the wafer transport device when the wafer transport devicesenses a rail mark on the transport rail.
 6. The method according toclaim 5, further comprising: acquiring an orientation information of theload port from the rail mark; and rotating the hoist unit based on theorientation information.
 7. The method according to claim 1, furthercomprising gripping a wafer container unit on the load port by the hoistunit, after lowering the hoist unit.
 8. The method of claim 1, furthercomprising determining an attitude of the hoist unit of the wafertransport device after lowering the hoist unit toward the load port. 9.The method of claim 1, wherein projecting the light beam onto the topsurface of the load port is such that the light beam projects a crosspattern on the top surface of the load port.
 10. A method comprising:moving a wafer transport device toward a process bay comprising a loadport; lowering a hoist unit of the wafer transport device above the loadport; determining an attitude of the hoist unit; and providing aresponse, by a controller, according to the determined attitude.
 11. Themethod according to claim 10, wherein the hoist unit and a predeterminedsurface have different attitudes, and providing the response comprises:raising the hoist unit; and sending the wafer transport device to amaintenance area.
 12. The method according to claim 10, wherein thehoist unit and a predetermined surface have substantially the sameattitude, and providing the response comprises operating a gripper ofthe hoist unit to grip or release a wafer container unit.
 13. The methodaccording to claim 10, wherein determining the attitude of the hoistunit comprises: measuring a first distance between a first position of atop surface of the hoist unit and a bottom surface of the wafertransport device; measuring a second distance between a second positionof a top surface of the hoist unit and the bottom surface of the wafertransport device; and comparing the first distance and the seconddistance.
 14. The method according to claim 13, wherein the top surfaceof the hoist unit is partitioned into eight sections by diagonal linesconnecting opposite corners of the top surface of the hoist unit andorthogonal lines connecting midpoints of opposite edges of the topsurface of the hoist unit, and the first position and the secondposition are respectively in two opposite sections of the top surface ofthe hoist unit.
 15. The method according to claim 10, wherein the wafertransport device has a plurality of belts, each of the belts isconnected to the hoist unit and wound around a respective belt windingdrum, and the method further comprises: raising the hoist unit; anddetermining a degree of winding of at least one of the belts around therespective belt winding drum.
 16. The method according to claim 15,wherein said at least one belt has a plurality of belt markings on aside thereof, and determining the degree of winding of at least one ofthe belts around the respective belt winding drum comprises: capturingan image of the belt markings; and comparing positions of the beltmarkings in the image with predetermined positions of the belt markings.17. The method according to claim 10, wherein the wafer transport devicehas a plurality of belts, each of the belts is connected to the hoistunit and wound around a respective belt winding drum, and determiningthe attitude of the hoist unit comprises measuring a tension of each ofthe belts.
 18. The method according to claim 17, wherein measuring atension of each of the belts comprises detecting sound waves from eachof the belts by using at least one acoustic sensor.
 19. A methodcomprising: stopping a wafer transport device above a load port having atop surface; after stopping the wafer transport device, rotating thewafer transport device; projecting a laser beam onto the top surface ofthe load port such that a laser line is formed on the top surface of theload port; comparing an orientation of the laser line with an edge ofthe top surface of the load port; rotating the wafer transport deviceagain based on the compared orientation of the laser line and the edgeof the top surface of the load port; and after rotating the wafertransport device again, lowering a hoist unit of the wafer transportdevice toward the load port.
 20. The method of claim 19, furthercomprising determining an attitude of the hoist unit of the wafertransport device after lowering the hoist unit of the wafer transportdevice toward the load port.